Return air pressure relief vent

ABSTRACT

A return air pressure relief vent comprising a baffle structure having two ports, disposed in a partition between two volumes of air and including a plurality of passages that each encompass a straight line extending between the two volumes of air, the plurality of passages structured and arranged to accommodate a pressure balancing flow of air between the two volumes of air while restricting the passage of sound and light.

FIELD OF THE INVENTION

[0001] This invention relates to a return air vent that permits pressurebalancing air flow while preserving sight and sound privacy.

BACKGROUND OF THE INVENTION

[0002] A central air system supplies conditioned air from a central airsupplier (air handler) through air supply ducts to various rooms andspaces located within a building. Conditioned air is returned to the airhandler from the various rooms and spaces through air return ducts.Conditioned air is heated or cooled, humidified or dehumidified in orderto maintain a comfortable environment within the building differing fromthe ambient conditions. The air handler re-conditions air returnedthrough the air return ducts and re-supplies the re-conditioned airthrough the air supply ducts to the various rooms and spaces within thebuilding.

[0003] Operation of the system can cause air pressure differencesbetween rooms and spaces within the building. These air pressuredifferences can reflect the relative amount of the flow of air suppliedby the air handler via air supply ducts and returned to the air handlervia air return ducts. When the system is balanced, an equal amount ofair is supplied by the air handler via the air supply ducts and returnedto the air handler via air return ducts.

[0004] A system providing the complete return of air to the air handlerprovides an air return duct in each room or space having an air supplyduct. This type of central air system maximizes the flow of conditionedair from the various rooms and spaces back to the air handler. This typeof system also minimizes pressure differences between rooms and spacessupplied with conditioned air and also reduces any unintentional comfortdifferences between rooms and spaces supplied with conditioned air tobetter enhance comfort within the building.

[0005] Unfortunately, it is common for building construction contractorsto reduce the cost of a central air system by constructing a systemproviding less than the complete return of air to the air handler. Thistype of system does not provide an air return duct for each room orspace having an air supply duct. Air supplied to rooms and spaceslacking a return duct typically causes air pressure to increase withinthat room or space. Increased air pressure within that room or spacecauses air to exit or leak from that room or space to other rooms orspaces having less air pressure and/or to exit or leak to the outsideatmosphere if the room is adjacent to an outside wall.

[0006] In an attempt to compensate for some of the disadvantages of asystem having a less than complete return of air to the air handler, airreturn ducts are typically placed in central locations (central returnducts) within the building to collect air that has exited or leaked fromrooms and spaces having an air supply duct but lacking an air returnduct. In this situation, rooms and spaces supplied with air effectivelyact as return ducts and their associated doors effectively act asobstacles to the flow of returned air. When these doors are closed, airis further restricted from flowing back to the centrally located returnducts. This causes pressure imbalances within the building and system tofurther increase. When these doors are open, sound and light privacy isreduced within each room and space associated with an open door.

[0007] Furthermore, air pressure in rooms and spaces where a centralreturn duct is located can drop below the air pressure in other spacesdue to a suction effect caused by the inability of the system to returnor draw back the amount of air supplied to the building.

[0008] Despite attempts to compensate for the disadvantages of a systemhaving a less than complete return of air to the air handler, such asystem typically has higher operating costs and continues to causeuneven air pressure and uneven heating or cooling of rooms and spaceswithin the building.

[0009] Even small air pressure differences between rooms and spaces cancause serious health and building maintenance problems. When a room isunder higher pressure than surrounding rooms or spaces, the air withinthe room leaks out of the room passing through any available hole orcrack.

[0010] If the building is in a heating climate, the warmer and moisterair of the room leaks out through walls and around windows and doors.When the warm and moist air strikes a surface within the wall structurethat is cooler than the dew point, the moisture in the leaking aircondenses out and onto surfaces inside the wall causing rot andenhancing the growth of mold. If the building is in a cooling climate,the suction effect of a room or space having an air return duct can drawwarm and moist air from the atmosphere through external walls of thebuilding to also cause rot and the growth of mold within the externalwalls of the building.

[0011] It has been shown that these types of problems can occur fromvery small pressure differences, for example from as low as a 2.5Pascals or 0.01 inches WC pressure difference between adjacent roomsand/or spaces. As a result, some jurisdictions, such as the State ofFlorida, have adopted stringent regulations that require new buildingswith central air systems to be designed and constructed to limitpressure differences between rooms to less than 2.5 Pascals.

BRIEF SUMMARY OF THE INVENTION

[0012] It is a further object of this invention to provide an improvedreturn air pressure relief vent that permits sufficient air flow tobalance pressure between two volumes of air while restricting thepassage of light and sound for the preservation of sight and soundprivacy.

[0013] It is a further object of this invention to provide an improvedreturn air pressure relief vent that complies with stringent buildingcodes.

[0014] It is a further object of this invention to provide an improvedreturn air pressure relief vent that is less expensive and simpler toinstall than the prior art.

[0015] It is a further object of this invention to provide an improvedreturn air pressure relief vent which wholly determines the pressurebalancing air flow between two volumes of air.

[0016] The invention results from the realization that a truly simpleand more effective return air pressure relief vent that balancespressure between two volumes of air can be effected by employing aplurality of passages that each encompass a straight line that extendsbetween the two volumes of air.

[0017] This invention features a return air pressure relief ventincluding a baffle structure having two ports. The baffle structure isdisposed in a partition between two volumes of air where each of the twoports confront each of the two volumes of air, respectively. The bafflestructure includes a plurality of passages, each of the plurality ofpassages encompasses a straight line extending between the two volumesof air. The plurality of passages are structured and arranged toaccommodate a pressure balancing flow of air between the two volumes ofair while restricting the passage of sound and light.

[0018] In some embodiments the partition is a wall separating two roomsor spaces within a building where each of the two rooms or spacesincludes one of the two volumes of air, respectively. In someembodiments the return air pressure relief vent permits 200 cubic feetper minute of air passage while limiting the pressure difference betweenthe two volumes of air to be less than 2.5 Pascal's.

[0019] In some embodiments, the return air pressure relief vent includesa frame configured to attach the plurality of passages to the partition.Optionally the frame includes an exterior surface extending between thetwo ports and the two volumes of air. The exterior surface can includeone or more rectangular and flat surfaces or alternatively can includeone or more curved surfaces.

[0020] In some embodiments the exterior surface of the frame includestwo sections which are sized to slide (telescope) into one another toadjust the width dimension of the frame. Optionally the frame caninclude a grill or a screen covering at least one of the two ports.Also, the grill can include a baffle member and the baffle member canoptionally include a plurality of louvers.In the preferred embodimentthe baffle includes passages that are provided by a honeycomb structureand a frame that is made of sheet metal. Preferably, the honeycombstructure is made from cardboard and the frame is made from sheet metalto reduce the cost of manufacture of each return air pressure reliefvent.

[0021] In some embodiments the plurality of passages have across-sections of circular shape. In other embodiments the plurality ofpassages have cross-sections of rectangular shape. Alternatively, theplurality of passages can have cross sections with a wide variety ofshapes and sizes.

[0022] In some embodiments the passages are parallel to each other. Inother embodiments the passages are not all parallel to each other.Optionally, the passages are perpendicular to a plane defined by theexterior surfaces of the partition. Alternatively, the passages are notperpendicular to a plane defined by the exterior surfaces of thepartition.

[0023] In some embodiments the plurality of passages each have across-section that varies in size or shape along a center line of thepassage extending between both volumes of air. In some embodiments theplurality of passages each have a cross-section not equal to the sizeand shape of the cross-sections of the other passages.

[0024] In some embodiments, the plurality of passages have a centerlineand an interior wall that are straight and parallel to each other. Inother embodiments, the plurality of passages have a centerline and aninterior wall that are not parallel to each other. In some embodimentsthe passages have a center line or an interior wall that is straight. Inother embodiments, the plurality of passages have a centerline and aninterior wall that is not straight.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Other objects, features and advantages will occur to thoseskilled in the art from the following description of a preferredembodiment and the accompanying drawings, in which:

[0026]FIG. 1 is a top-down view of a partition separating two volumes ofair.

[0027]FIG. 2 is a side view of an embodiment of the baffle structurecomprising a port and a plurality of passages having hexagonalcross-sections as disposed within a partition according to an embodimentof the invention.

[0028]FIG. 3A is a side view of an embodiment of the baffle structurecomprising a plurality of passages having hexagonal cross-sections thatare disposed within a frame having a rectangular exterior surface.

[0029]FIG. 3B is a side view of an embodiment of the baffle structurecomprising a plurality of passages having hexagonal cross-sections thatare disposed within a frame having a curved exterior surface.

[0030]FIG. 4 is a side view of an embodiment of the baffle structurecomprising a port, a frame and a grill according to an embodiment of theinvention.

[0031]FIG. 4A is a perspective view of an embodiment of the framecomprising two telescoping portions that are each attached to a separategrill.

[0032]FIG. 4B is a perspective view of a portion of an embodiment of theframe attached to a screen.

[0033]FIG. 5 is a side view of paths of air flow through an embodimentof the baffle structure having passages that are perpendicular to aplane defined by the partition.

[0034]FIG. 6 is a side view of the paths of air flow through anembodiment of the baffle structure having passages that are notperpendicular to a plane formed by the partition.

[0035]FIG. 7 is a side view of the paths of air flow through anembodiment of the baffle structure having passages that are also notperpendicular to a plane formed by the partition.

[0036]FIG. 8 is a side view of the paths of air flow through anembodiment of the baffle structure having passages that are not parallelto each other.

[0037]FIG. 9 is a side view of an embodiment of the baffle structurecomprising a port and a plurality of passages having circularcross-sections as disposed within a partition according to an embodimentof the invention.

[0038]FIG. 10 is a side view of an embodiment of the baffle structurecomprising a port and a plurality of passages having rectangularcross-sections as disposed within a partition according to an embodimentof the invention.

[0039]FIG. 11 is a side view of an embodiment of the baffle structurecomprising a plurality of passages that each have a straight centerline, a straight interior wall and a cross-section that varies in sizealong each center line.

[0040]FIG. 12 is a side view of an embodiment of the baffle structurecomprising a plurality of passages that each have a curved center lineand a curved interior wall that are parallel to each other.

PREFERRED EMBODIMENT

[0041] Aside from the preferred embodiment or embodiments disclosedbelow, this invention is capable of other embodiments and of beingpracticed or being carried out in various ways. Thus, it is to beunderstood that the invention is not limited in its application to thedetails of construction and the arrangements of components set forth inthe following description or illustrated in the drawings.

[0042] Partition 110 (FIG. 1) separates volume A of air 120 from volumeB of air 130. Volumes of air A 120 and B 130 can each represent a roomor space within a building separated by the partition 110 representing awall within the same building.

[0043] For reference, the X and Y axes are directed parallel to thepartition, and the Z-axis is directed perpendicular to the partition.The Y-axis is directed parallel to the top to bottom viewing perspectivewhile the X axis is directed perpendicular to the Y.

[0044] The baffle structure 240 (FIG. 2) is disposed within partition110 between two volumes of air 120, 130. The baffle structure 240comprises a plurality of passages that each encompasses a straight linethat extends between the two volumes of air 120, 130 (See FIG. 5).

[0045] Each of the plurality of passages within baffle structure 240 hastwo opposite and open ends. The ends of the passages on one side ofpartition 110 as shown in FIG. 2 comprise port A 242 of baffle structure240. The ends of the passages on the opposite side of partition 110 thatare not directly shown in FIG. 2 comprise port B 242B of bafflestructure 240.

[0046] In this embodiment, the plurality of passages are formed by ahoneycomb structure. Each passage has a hexagonal cross-section at eachend and along the interior wall extending between each end and the twovolumes of air 120, 130. The interior wall of each passage extends alonga straight line between each end and between the two volumes of air 120,130. The shape and the size of the cross-section of each passage at eachend is the same (constant) for each of the plurality of passages. Theshape and the size of the cross-section of each passage does not varyalong the interior wall of the passage extending between each end andbetween the two volumes of air 120, 130.

[0047] For other embodiments, other structures can be used to form thesepassages. Also, the shape or size of the cross-section of each passageat each end can vary between each of the plurality of passages.Furthermore, the shape or the size of the cross-section of each passagecan vary along the interior wall of the passage extending between eachend and between the two volumes of air 120, 130.

[0048] Each cross-section of each passage as measured at each end or asmeasured along the interior wall between each end of each passage, has acenter point. The plurality of center points of the cross-sections ofeach passage as measured along the interior wall between each end formsa center line of each passage. In this embodiment, the center line ofeach passage is straight and parallel to its interior wall. In otherembodiments, the center line may or may not be straight and may or maynot be parallel to the interior wall of each passage.

[0049] The plurality of passages within baffle structure 240 arestructured and arranged to accommodate air flow and to simultaneouslyrestrict the passage of sound and light between the two volumes of air120 and 130. Air flow through the baffle structure 240 enables anydifference in air pressure between the two volumes of air 120 and 130 toequalize (balance).

[0050] This embodiment can be used as a vent between two rooms and/orspaces within a building to allow air to pass between one room or spaceand another room or space while restricting the passage of light andsound between those rooms and/or spaces. In this embodiment, eachpassage is shown to have a cross section that is hexagonally shaped(six-sided) and uniformly sized. The cross-section of each passage canbe one of a variety of many shapes or sizes.

[0051] A central air system typically passes 50 to 200 cubic feet of airper minute through an air supply duct into a room or space. Generally,the larger the cross-sectional area of air passage provided by the ports242A, 242B of a baffle structure, the smaller the pressure differencerequired between both ports 242A, 242B for the baffle structure 240 topass a particular amount of air flow between volumes A 120 and B 130.

[0052] To limit pressure differences between two volumes of air 120, 130to less than 2.5 Pascals while allowing 150 cubic feet per minute of airpassage through the baffle structure 240, the cross-sectional area ofair passage of the baffle structure 240 should approximate at least 140square inches. For example, the embodiment shown in FIG. 2 with a twelveinch by twelve inch cross-section for each port 242A, 242B would allow150 cubic feet per minute of air to pass through the baffle structurewhile limiting the pressure difference between each port 242A, 242B toless than 2.5 Pascals.

[0053] The frame 246 (FIG. 3A) encloses the plurality of passages andenables the baffle structure 240 to be properly fitted and aligned intoan opening within a partition 110. The partition 110 can be an interiorwall of a building. Port B 242B is not directly shown from thisperspective.

[0054] Frame 246 is preferably made of sheet metal or plastic material.There is no requirement that the frame function as a structural memberof the partition 110. Frame 246 preferably has two lips 248 a and 248 beach having an outer surface that are each parallel to a proximate outersurface of the partition 110. The distance between frame lips 248 a and248 b is preferably equal to the width dimension (parallel to the Zaxis) of the partition 110 to enable a snug and flush fit between theframe 246 and the partition 110. In some embodiments, the distancebetween the lips 248 a and 248 b is adjustable as shown in FIG. 5.

[0055] Preferably, to limit the cost of each installation, the frame 246is constructed from sheet metal and the plurality of passages areconstructed from cardboard. Many other materials can be used toconstruct either the frame and/or the plurality of passages.

[0056] The embodiment of a frame 246 having a curved exterior surface252 (FIG. 3B) encloses the plurality of passages and enables the bafflestructure 240 to be properly fitted and aligned into an opening within apartition 110. The partition 110 can be an interior wall of a building.Port B 242B is not directly shown from this perspective.

[0057] The grill 250 (FIG. 4) functions as a decorative cover to thebaffle structure 240. Grill 250 encloses port A 242 while allowing thepassage of air flow. Port B 242B is not directly shown from thisperspective. Optionally, grill 250 can have a plurality of louvers thatredirect airflow traveling through baffle structure 240.

[0058] An embodiment of the frame 246 comprises two telescoping exteriorsurfaces 252A, 252B (FIG. 4.A) that each have separate lips 248A, 248Brespectively, and that optionally attach to a separate grill 250A, 250B.Exterior surface 252B of the frame 246 is manufactured to have aslightly larger exterior perimeter than that of the exterior surface252A of the frame 246. Exterior surface 252B is designed to fit outsideof and slide over exterior surface 252A to enable the width dimension(parallel to the Z axis) of the frame 246 to be adjustable.

[0059] Optionally, the frame 246 (FIG. 4A) can include portions whichare sized to slide (telescope) into one another to adjust the widthdimension (Z dimension, FIG. 1) of the frame 246. The width dimension ofthe frame 246 can be adjusted to the width dimension of the partition110. As shown this embodiment, the frame 246 can optionally includegrills 250A and 250B that are disposed on opposite sides of thepartition 110 (not shown).

[0060] An embodiment of the baffle structure comprises a frame 246 and ascreen 254 (FIG. 4B). The screen 254 filters particulate matter from theair flowing through the baffle structure 246. As shown, the screen 254covers port A 242 of the baffle structure and partially covers lip 248 aof the frame 246. Optionally, the screen can partially cover or entirelycover the lip 248 a of the frame 246. The screen 254 can be manufacturedfrom a variety of materials (typically metal or plastic) that filterparticulate matter located within the air. Optionally the screen 254 canbe further covered by a grill 250 to effect an appearance shown in FIG.4.

[0061] Air flows through the plurality of passages of the bafflestructure 240 (FIG. 5). In this embodiment, the plurality of passagesare directed straight and parallel to each other. Each passageencompasses a straight line 580A, 580B, 580C extending between the twovolumes of air 120, 130. The center line 590A, 590B, 590C and theinterior wall 570A, 570B, 570C, 570D of each passage is straight andparallel to each other and parallel to the center line 590A, 590B, 590Cand interior walls 570A, 570B, 570C, 570D of the other passages. Thecenter line 590A, 590B, 590C and interior wall 570A, 570B, 570C, 570D ofeach passage are directed along straight lines that are perpendicular tothe plane that is parallel to the opposing surfaces of the partition110.

[0062] Preferably, the plurality of passages are formed by a honeycombstructure like that shown in FIG. 2. Straight and parallel passages,such as those formed by a honeycomb structure, provide low resistance toair flow and provide an added benefit of reducing the air turbulance ofair flow exiting the baffle structure 240 relative to that of the airflow entering the baffle structure 240.

[0063] In some embodiments (FIGS. 6 and 7), the plurality of passagesare directed straight and parallel to each other and along straightlines that are not perpendicular to a plane that is parallel to theopposing surfaces of the partition 110. Each passage encompasses astraight line (not shown) extending between the two volumes of air 120,130 (FIGS. 1 and 5).

[0064] These embodiments can be used to direct air exiting from thebaffle structure 240 in the upward or downward direction as desired. Theport 242A, 242B from which air is desired to enter the baffle structure240 is placed on the side of the partition 110 having an air supply ductand/or not having an air return duct. The port from which air is desiredto exit the baffle structure 240 is placed on the side of the partition110 having the lower air pressure during the operation of the centralair system.

[0065] In some embodiments (FIG. 8), the plurality of passages aredirected between ports 242A, 242B along straight lines that are notparallel to each other and that are not necessarily perpendicular to aplane that is parallel to the opposing surfaces of the partition 110.Each passage encompasses a straight line (not shown) extending betweenthe two volumes of air 120, 130.

[0066] In some embodiments, the passages of the baffle structure 240(FIG. 9) have circular cross-sections. Each passage encompasses astraight line (not shown) extending between the two volumes of air 120,130. The plurality of passages shown function in the same manner as theplurality of the passages shown in FIG. 2. The cross-sectional surfacearea of the openings of the passages should preferably be greater than90% of the total cross-sectional area comprising the openings of thepassages and the material forming the walls of the passages.

[0067] In some embodiments, the passages of the baffle structure 240(FIG. 10) have rectangular cross-sections. Each passage encompasses astraight line 580A, 580B, 580C extending between the two volumes of air120, 130. The plurality of passages shown function in the same manner asthe plurality of the passages shown in FIG. 2.

[0068] In some embodiments, the passages of the baffle structure 240(FIG. 11) each comprises a plurality of passages that each havecross-sections that vary in size along a its center line extendingbetween ports 242A and 242B and volumes of air 120, 130. Each passageencompasses a straight line (not shown) extending between the twovolumes of air 120, 130. The center point of each cross-section of thepassage between its two ends forms a straight center line between port A242A and port B 242B and the volumes of air 120, 130. The plurality ofpassages shown function in the same manner as the plurality of thepassages shown in FIG. 2.

[0069] Preferably, the baffle structure 240 is oriented so that port A242A is the port from which air is likely to exit. Preferably, port A isplaced on the side of the partition 110 having lower air pressure duringthe operation of the central air system. In some embodiments, each ofthe plurality of passages of the baffle structure 240 (FIG. 12) has acenter line 1290 and an interior wall 1270 that is not straight. Each ofthe plurality of passages encompasses a straight line 1280 extendingbetween both ports 242A, 242B and the two volumes of air 120, 130. Thecenter point of each cross-section of the passage along its interiorwall 1270 extending between its two ends forms a center line 1280 thatis curved and not straight.

[0070] The embodiments of the return air pressure relief vent describedare designed to permit a sufficient flow of air (150 cubic feet perminute) between two rooms or spaces to accommodate return air flow for acentral air system while limiting the air pressure difference betweenthe two rooms or spaces to be less than 2.5 Pascals. Furthermore, theseembodiments are designed to restrict the passage of sound and lightbetween the two rooms or spaces.

[0071] Although specific features of the invention are shown in somedrawings and not in others, this is for convenience only as each featuremay be combined with any or all of the other features in accordance withthe invention. The words “including”, “comprising”, “having”, and “with”as used herein are to be interpreted broadly and comprehensively and arenot limited to any physical interconnection. Moreover, any embodimentsdisclosed in the subject application are not to be taken as the onlypossible embodiments.

[0072] Other embodiments will occur to those skilled in the art and arewithin the following claims:

What is claimed is:
 1. A return air pressure relief vent comprising: abaffle structure having two ports and disposed in a partition betweentwo volumes of air, each of said two ports confronting each of said twovolumes of air respectively; and said baffle structure including aplurality of passages, each of said plurality of passages encompasses astraight line extending between said two volumes of air, said pluralityof passages structured and arranged to accommodate a pressure balancingflow of air between said two volumes of air while restricting thepassage of sound and light.
 2. The return air pressure relief vent ofclaim 1 in which said partition is a wall separating two rooms or spaceswithin a building and where each of said two rooms or spaces includesone of said two volumes of air respectively.
 3. The return air pressurerelief vent of claim 2 where the return air pressure relief vent permits150 cubic feet per minute of air passage while limiting the pressuredifference between the two volumes of air to less than 2.5 Pascals. 4.The return air pressure relief vent of claim 1 in which the bafflestructure includes a frame configured to attach the plurality ofpassages to the partition.
 5. The return air pressure relief vent ofclaim 4 in which said frame includes an exterior surface extendingbetween said two ports.
 6. The return air pressure relief vent of claim5 in which said exterior surface comprises one or more rectangular andflat surfaces.
 7. The return air pressure relief vent of claim 5 inwhich said exterior surface comprises one or more curved surfaces. 8.The return air pressure relief vent of claim 5 in which said exteriorsurface includes two sections which telescope into one another to adjustthe width dimension of said frame.
 9. The return air pressure reliefvent of claim 4 in which said frame includes a grill covering at leastone of the two said ports.
 10. The return air pressure relief vent ofclaim 9 in which said grill includes a baffle member.
 11. The return airpressure relief vent of claim 10 in which said baffle member includes aplurality of louvers.
 12. The return air pressure relief vent of claim 9in which said grill includes a screen.
 13. The return air pressurerelief vent of claim 1 in which said baffle structure includes ahoneycomb structure, said honeycomb structure including at least some ofthe said plurality of passages.
 14. The return air pressure relief ventof claim 1 in which at least some of said plurality of passages have acircular cross-section.
 15. The return air pressure relief vent of claim1 in which at least some of said plurality of passages are not parallelto other of said plurality of passages.
 16. The return air pressurerelief vent of claim 1 in which at least some of said plurality ofpassages are not perpendicular to a plane defined by the exteriorsurfaces of the partition.
 17. The return air pressure relief vent ofclaim 1 in which said frame is made from sheet metal.
 18. The return airpressure relief vent of claim 1 in which at least some of said pluralityof passages have a cross-section that varies in size or shape along acenter line of the passage extending between both ports of the bafflestructure.
 19. The return air pressure relief vent of claim 1 in whichat least some of said plurality of passages have a cross-section notequal to the size and shape of a cross-section of other of saidplurality of passages.
 20. The return air pressure relief vent of claim1 in which said plurality of passages are constructed from a honeycombstructure manufactured from cardboard.
 21. The return air pressurerelief vent of claim 1 in which at least some of said plurality ofpassages have a center line and an interior wall that are straight andparallel to each other.
 22. The return air pressure relief vent of claim1 in which at least some of said plurality of passages have a centerline and an interior wall that are not parallel to each other.
 23. Thereturn air pressure relief vent of claim 1 in which at least some ofsaid plurality of passages have a center line or an interior wall thatis straight.
 24. The return air pressure relief vent of claim 1 in whichat least some of said plurality of passages have a center line or aninterior wall that is not straight.